共查询到19条相似文献,搜索用时 296 毫秒
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为了研究大气湍流对自由空间量子密钥分发的性能影响,将大气湍流建模为空间中随机分布的空气球泡,利用几何光学原理分析单光子在湍流球泡中的传播,定量计算了经过两次折射后由于偏振态变化造成的光子透射率比值k和误码率Ep的起伏,利用蒙特卡洛方法模拟了湍流折射率随机变化时二者的趋势;最后推导了经过湍流折射后的诱骗态空间量子密钥分发成码率公式并通过分析误码来源得到满足成码率需要的k值上限,建立偏振误码率与入射角和湍流折射率的关系并得到Ep的安全阈值.仿真结果表明当入射角在44.8°~76.5°,湍流折射率在1~1.33范围内可以满足误码率的上限约束.该研究为湍流条件下进行空间量子通信实验提供了理论参考. 相似文献
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近年来, PM2.5大气污染日益严重, 不仅影响空气质量与大气能见度, 而且还会对自由空间量子光信号的传输造成影响. 然而, 有关PM2.5与自由空间量子通信信道参数关系的研究, 迄今尚未展开. 本文根据PM2.5粒度谱分布函数及其化学成分的消光份额, 提出了PM2.5指数、大气湿度与自由空间量子信道衰减的关系; 针对幅值阻尼信道和退极化信道, 分别建立了PM2.5污染程度与信道容量、信道平均保真度、信道误码率的定量关系. 仿真结果表明, 当大气湿度为30%, PM2.5指数分别为50和300时, 自由空间量子通信信道容量、信道平均保真度、信道误码率分别依次为0.83和0.21, 0.91和0.56, 0.0048和0.0192. 由此可见, PM2.5污染程度对自由空间量子通信性能有显著的影响. 因此, 为了提高自由空间量子通信的可靠性, 应根据PM2.5大气污染状况, 自适应调整系统的各项参数. 相似文献
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基于泊松分布单光子源的量子误码率的分析 总被引:1,自引:0,他引:1
在自由空间量子密钥分配中,单光子源采用具有泊松分布的高度衰减激光脉冲,量子密码术协议采用BB84和B92协议。通过引入量子信道传输率、单光子捕获概率、测量因子和数据筛选因子,建立了量子误码率理论模型,给出了量子误码率的表达式。对于自由空间量子信道,引起量子误码率的主要因素是光学元件、探测器暗噪声和空间光学环境,并对这些因素进行了分析。针对低轨卫星_地面站间链路,进行了量子误码率的数值仿真研究。结果表明,在低轨卫星_地面站间进行量子密钥分配是可行的,限制自由空间量子密钥分配链路距离的主要因素是探测器暗噪声和空间光学环境。 相似文献
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为了研究近地面大气湍流对自由空间量子通信的影响,基于近地面大气湍流的Tunick模型,得到湍流气象参数与量子信道纠缠度之间的关系,针对量子退极化信道和幅值阻尼信道,建立湍流气象参数与信道容量之间的方程,分析湍流对量子信道利用率的影响,并进行性能仿真.结果表明:当压强为100kPa,风速为2m/s,温度为25℃,相对湿度分别为0.2和0.6时,量子信道的纠缠度分别为0.27和0.18,退极化信道容量分别为0.951 6和0.946 5,幅值阻尼信道容量分别为0.439 0和0.422 7,量子信道利用率分别为0.42和0.37.量子通信信道的各种参数与近地面大气湍流的气象参数有紧密联系,根据近地面大气湍流的气象参数,自适应调整量子通信系统的各项参数,可以提高量子通信的可靠性. 相似文献
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大气湍流及瞄准误差联合效应下自由空间光通信的性能 总被引:1,自引:0,他引:1
研究了Gamma-Gamma大气湍流信道下闪烁和瞄准误差联合效应对自由空间光通信的性能影响。假定自由空间光通信系统采用开关键控(OOK)强度调制直接探测(IM/DD),推导得出了系统的误码率和中断概率闭合表达式,分析了大气湍流、归一化波束宽度、平均发射功率、归一化的抖动标准差、信噪比等参数对系统性能的影响。基于推导的闭合表达式进行了数值模拟,结果表明能够在给定发射功率下通过优化波束宽度使系统性能达到最优。 相似文献
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大气湍流引起的光强闪烁使得自由空间光通信(FSO)系统性能恶化,而分集接收技术可有效改善这一影响。为进一步分析分集接收技术对相干接收系统性能的影响,基于二进制相移键控(BPSK)调制和外差相干接收技术,建立了Gamma-Gamma大气湍流信道模型下自由空间光通信分集接收系统模型。在不同大气湍流强度和接收天线数情况下,分别采取最大比合并(MRC)、选择合并(SC)和等增益合并(EGC),分析了对应的系统误码率(BER)和通信中断概率(OP),并与相同接收口径下的传统单天线接收系统的性能进行了比较。结果表明:MRC、EGC分集接收对大气湍流下的相干通信系统性能有明显改善,而SC分集接收仅当平均信噪比低于某一阈值时对相干通信系统的性能有所优化。 相似文献
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Tianyi Wu Qing Pan Chushan Lin Lei Shi Shanghong Zhao Yijun Zhang Xingyu Wang Chen Dong 《Entropy (Basel, Switzerland)》2021,23(9)
Polarization encoding has been extensively used in quantum key distribution (QKD) implementations along free-space links. However, the calculation model to characterize channel transmittance and quantum bit error rate (QBER) for free-space QKD has not been systematically studied. As a result, it is often assumed that misalignment error is equal to a fixed value, which is not theoretically rigorous. In this paper, we investigate the depolarization and rotation of the signal beams resulting from spatially-dependent polarization effects of the use of curved optics in an off-axis configuration, where decoherence can be characterized by the Huygens–Fresnel principle and the cross-spectral density matrix (CSDM). The transmittance and misalignment error in a practical free-space QKD can thus be estimated using the method. Furthermore, the numerical simulations clearly show that the polarization effect caused by turbulence can be effectively mitigated when maintaining good beam coherence properties. 相似文献
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Chang-Hua Zhu Dong-Xiao Quan Fang Zhang Chang-Xing Pei 《International Journal of Theoretical Physics》2013,52(2):596-603
We investigate the key rate of polarization-coded optical fiber-based quantum key distribution system (QKD) with BB84 protocol by channel tomography. The quantum bit error rate (QBER) of the QKD system under depolarizing channel is obtained by analyzing output density operators, transmission rate of channel, transmission rate of the receiver and dark count of single photon detector. According to the estimated QBER an LDPC chosen adaptively is applied to information reconciliation and the practical final key rate is discussed. Analysis results show that compared with cascade scheme and no channel knowledge the key rate can be improved by the proposed reconciliation scheme with channel tomography. 相似文献
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Qing-Lin Wu Er-Long Miao Yun Liu Yi-Min Dai Guang-Can Guo 《Optics Communications》2007,275(2):486-490
In this paper, it is investigated that how the atmosphere effects on the synchronization accuracy in free-space quantum key distribution (QKD). We measured the synchronization error of a free-space QKD in our near-ground platform. According to experimental results and theoretical calculations, we deduce that the intensity fluctuation of synchronization light due to atmosphere disturbance contributes far more to the synchronization accuracy than others. By using the constant fraction discrimination method, the synchronization error of the free-space QKD, passing through the aerosphere, can be limited within 300 ps which meets the synchronization requirement of a satellite-to-ground QKD system. 相似文献
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E. O. Kiktenko A. O. Malyshev A. A. Bozhedarov N. O. Pozhar M. N. Anufriev A. K. Fedorov 《Journal of Russian Laser Research》2018,39(6):558-567
Quantum key distribution (QKD) offers a practical solution for secure communication between two distinct parties via a quantum channel and an authentic public channel. In this work, we consider different approaches to the quantum bit error rate (QBER) estimation at the information reconciliation stage of the post-processing procedure. For reconciliation schemes employing low-density parity-check (LDPC) codes, we develop a novel syndrome-based QBER estimation algorithm. The algorithm suggested is suitable for irregular LDPC codes and takes into account punctured and shortened bits. Testing our approach in a real QKD setup, we show that an approach combining the proposed algorithm with conventional QBER estimation techniques allows one to improve the accuracy of the QBER estimation. 相似文献
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Cryptanalysis of Multiparty Quantum Secret Sharing of Quantum State Using Entangled States 下载免费PDF全文
Security of a quantum secret sharing of quantum state protocol proposed by Guo et al. [Chin. Phys. Lett. 25 (2008) 16] is reexamined. It is shown that an eavesdropper can obtain some of the transmitted secret information by monitoring the classical channel or the entire secret by intercepting the quantum states, and moreover, the eavesdropper can even maliciously replace the secret message with an arbitrary message without being detected. Finally, the deep reasons why an eavesdropper can attack this protocol are discussed and the modified protocol is presented to amend the security loopholes. 相似文献
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Decoy state quantum key distribution (QKD), being capable of beating PNS attack and being unconditionally secure has become attractive recently. However, in many QKD systems, disturbances of transmission channel make the quantum bit error rate (QBER) increase, which limits both security distance and key bit rate of real-world decoy state QKD systems. We demonstrate the two-intensity decoy QKD with a one-way Faraday- Michelson phase modulation system, which is free of channel disturbance and keeps an interference fringe visibility (99%) long period, over a 120 km single mode optical fibre in telecom (1550nm) wavelength. This is the longest distance fibre decoy state QKD system based on the two-intensity protocol. 相似文献
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We report on the implementation of a Bennett-Brassard 1984 quantum key distribution protocol over a free-space optical path on an optical table. Attenuated laser pulses and Pockels cells driven by a pseudorandom number generator are employed to prepare polarization-encoded photons. The sifted key generation rate of 23.6 kbits per second and the quantum bit error rate (QBER) of 3% have been demonstrated at the average photon number per pulse μ = 0.16. This QBER is sufficiently low to extract final secret keys from shared sifted keys via error correction and privacy amplification. We also tested the long-distance capability of our system by adding optical losses to the quantum channel and found that the QBER remains the same regardless of the loss. 相似文献